Explicitly set tag/label

Author: sourcefrog

.github/workflows/container.yml

@@ -47,10 +47,8 @@ jobs:
         uses: docker/build-push-action@v6
         with:
           push: true
-          tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
-        env:
-          SOURCE_DATE_EPOCH: 0
+          tags: sourcefrog/cargo-mutants:latest  # ${{ steps.meta.outputs.tags }}
+          labels: latest # ${{ steps.meta.outputs.labels }}
 
       - name: Generate artifact attestation
         uses: actions/attest-build-provenance@v2